An eye is largely divided into an eyeball and ocular adnexa. The eyeball includes an outer membrane, a middle membrane, an inner membrane, and contents, and the ocular adnexa includes an orbit of an eye, a conjunctiva, and the like. Among these, the outer membrane and the conjunctiva form a boundary between the eye and the outer world.
The cornea is a transparent membrane that forms the surface of the eyeball. The conjunctiva is a mucosal membrane that connects the eyeball with an eyelid and is divided into a conjunctiva palpebrarum and a bulbar conjunctiva. Meanwhile, a transition part of the cornea and the bulbar conjunctiva is referred to as a limbus corneae, and a transition part of the bulbar conjunctiva and the conjunctiva palpebrarum is referred to as a fornix conjunctiva.
Dry eye syndrome, also known as keratoconjunctivitis sicca or dysplasia, is a common disease, which is a type of ophthalmic disorder, affecting a large number of people. In the United States, approximately 5 million people among a population over the age of 50 are estimated to have severe dry eye syndrome (Schaumberg et al., Am J Ophthalmol 2003; 136 (2): 318-326).
Symptoms of dry eye syndrome include burning, dryness, redness, itching, persistent irritation, and the like. Dry eye syndrome, when severe, may damage eyesight and cause difficulty in performing vision-critical tasks, such as studying, reading, and driving. Dry eye syndrome may be a symptom of other diseases, rather than mere dry eye syndrome itself. Typically, the symptoms may be manifested in Sjögren's syndrome. In addition, with age, moisture of the lacrimal gland may decrease, which leads to eye dryness, congestion, itching, and a foreign object feeling, therefore dry eye syndrome often appears as a symptom of aging.
Dry eye syndrome is a multifactorial disorder that is accompanied by symptoms of eye discomfort, visual disturbance, instability of the tear film, and damage of the ocular surface caused by an insufficient amount of tears or abnormality of a tear component, involving an increase in the tear film osmolarity and inflammation on the ocular surface (an increase in inflammatory cytokines) (Behrens A, Doyle J J, Stern L, et al.; Dysfunctional tear syndrome study group. Dysfunctional tear syndrome: a Delphi approach to treatment recommendations. Cornea 2006; 25: 900-907), (Lemp M A, Baudouin C, Baum J, et al. The definition and classification of dry eye disease: report of the definition and classification subcommittee of the international dry eye workshop (2007). Ocul Surf 2007; 5: 75-92).
Various methods of treating dry eye syndrome are known. Dry eye syndrome is managed with nonpharmacologic treatments including exacerbating factor avoidance, eyelid hygiene, tear supplementation, secretagogues, a punctual plug, an anti-inflammatory agent, a moisture chamber, and other environmental management and pharmacologic treatments (Behrens et al., Dysfunctional tear syndrome study group. Dysfunctional tear syndrome: a Delphi approach to treatment recommendations. Cornea 2006; 25(8): 900-907).
Among the various methods of treating dry eye syndrome, pharmacological treatment is accompanied by many shortcomings. For example, artificial tear solutions are very cumbersome to use due to having highly temporary effects, which requires the patient to repeatedly administer the artificial solution. In addition, increasing the viscosity of the artificial tear solution may prolong the duration of the artificial tear solution in the eyeball but may cause stickiness in the eyes, which in turn leads to deterioration of feeling in use. In addition, administration of topical steroids leads to development of side effects, such as increased intraocular pressure, glaucoma, cataracts, and worsening of corneal infections.
Meanwhile, eye tracker technology capable of tracking and monitoring eye movement in performing a certain affair or task has been introduced.
However, such an eye tracker is inconvenient due to the need for wearing, attaching, or installing a separate device, so there is an imperative need to develop a technique capable of preventing dry eye syndrome without causing inconvenience to a user.